The Olive Oil Tree: What Olea Europaea Actually Is
If you have searched for the olive oil tree, you are almost certainly looking for one plant: Olea europaea, the olive. There is no separate species grown for oil and another grown for the table — the same tree gives both, and which you get depends on the cultivar and on what the grower decides to do with the fruit. What makes the tree worth understanding is that nearly every decision shaping a bottle of oil is taken out in the grove, sometimes years before anything reaches a mill. This guide covers what the olive tree actually is, how botanists classify it, how long it takes to bear, why its crop swings from one season to the next, and why nobody can honestly tell you how old the famous ancient trees are.
For our own oil, see our cold-pressed organic Marrakech olive oil.
The Short Answer
- The olive oil tree is Olea europaea L., in the family Oleaceae — one species, first published by Linnaeus in Species Plantarum in 1753. There is no separate oil species.
- Kew's Plants of the World Online, the taxonomic register of record, currently accepts seven subspecies. You will very often read six — including on Kew's own narrative species page, which its taxonomic backbone contradicts.
- The named oils on a shelf — Picual, Koroneiki, Arbequina, Manzanilla Cacereña — are cultivars, not botanical varieties. That is a real distinction, and the two are governed by different codes of nomenclature.
- Olives are slow to come into bearing, and once bearing they tend to alternate: a heavy crop one year followed by a light one the next. This is called alternate bearing, and it is the single biggest reason olive oil supply and price move about.
- The wild olive or oleaster, usually written var. sylvestris, is not an accepted taxon at Kew at all. It is treated as a synonym and folded into subsp. europaea.
- Nobody can reliably date a living ancient olive. Olive wood cannot be ring-counted, and radiocarbon work on living trees finds datable internal wood rarely older than about 300 years.
- Sidr & Stone's oil comes from one rain-fed, organically grown family grove on the plains outside Marrakech, harvested once a season and cold-pressed within hours.
What "Olive Oil Tree" Actually Refers To
The phrase is slightly malformed, and worth straightening out before anything else. There is no tree called the olive oil tree. There is the olive tree, and olive oil is what you get when you crush its fruit. Kew's Plants of the World Online gives the accepted name as Olea europaea L., first published in Species Plantarum in 1753, in the family Oleaceae, and records its native range as Africa and the Mediterranean through to south-central China.
It is an evergreen shrub or tree that Kew describes as growing to around 15 metres, with narrow leathery leaves borne in opposite pairs — dark green above, silvery-scaled beneath, which is what gives a grove its shimmer in wind. The flowers are small, white and four-lobed, carried in clusters where the leaf meets the stem. The fruit is a drupe: a fleshy layer around a hard stone. It is that fleshy layer, not the seed, that holds the oil. If you have met the Latin name on a cosmetics label rather than in a grove, our guide to what Olea europaea oil means on a label covers that side of it.
The Subspecies Kew Accepts — and Why You Will Read a Different Number
Here is a genuine oddity, and it is worth being straight about it. Kew's taxonomic backbone — the World Checklist of Vascular Plants, which is the register serious botanists key to — lists seven accepted subspecies of Olea europaea. Kew's own narrative species profile, on the same website, says "Six genetically distinct subspecies are currently recognised" and gives subsp. cuspidata a range across eastern and southern Africa. The backbone does not. It puts every African population under subsp. africana, and confines cuspidata to Asia and Arabia.
Where a register disagrees with its own narrative prose, the register wins. The seven accepted subspecies, with the native ranges exactly as Kew states them:
| Subspecies | Author | Native range, as Kew states it |
|---|---|---|
| subsp. europaea | (autonym) | "as a cultigen from the Medit." — the cultivated olive and its feral escapes |
| subsp. africana | (Mill.) P.S.Green | "Eritrea to S. Africa" |
| subsp. cuspidata | (Wall. ex G.Don) Cif. | "Arabian Pen. to China (Yunnan)" |
| subsp. laperrinei | (Batt. & Trab.) Cif. | "Sahara" — Algeria, Niger and Sudan |
| subsp. maroccana | (Greuter & Burdet) P.Vargas et al. | "Morocco (S. High Atlas)" |
| subsp. guanchica | P.Vargas, J.Hess, Muñoz Garm. & Kadereit | "Canary Is." |
| subsp. cerasiformis | G.Kunkel & Sunding | "Madeira" |
Two of those are worth pausing on. Subsp. laperrinei survives on isolated Saharan massifs, and subsp. maroccana as a small population at the southern end of Morocco's High Atlas — relict populations, hundreds of miles from any commercial grove. Note also that cerasiformis is the Madeiran one and guanchica the Canarian one; they are easy to swap, and frequently are.
Cultivar, Variety, and the Wild Olive
Almost everyone writing about olive oil uses "variety" loosely, and it is usually harmless. But the words mean different things, and the difference explains why the olive world is so full of duplicated and contradictory names.
| Term | What it means | Governed by | Example |
|---|---|---|---|
| Species | The basic unit — one interbreeding kind of plant | Botanical code (ICN) | Olea europaea |
| Subspecies | A geographically distinct wild population within the species | Botanical code (ICN) | subsp. laperrinei |
| Botanical variety | A rank below subspecies, for naturally occurring forms | Botanical code (ICN) | var. sylvestris — but see below |
| Cultivar | A human selection, kept distinct, uniform and stable by propagation | Cultivated plant code (ICNCP) | 'Picual', 'Koroneiki', 'Arbequina' |
A cultivar name is written in single quotes, never italicised, and it is a clone: every 'Picual' tree in Spain descends by cutting or graft from the same original selection. That is why cultivar matters to the taste of an oil in a way subspecies never will — it is the level at which humans actually chose. Kew notes there are over 1,000 cultivars of olive, all with far larger, fleshier fruit than their wild ancestor.
And the wild ancestor is where the tidy picture breaks. The oleaster — the wild olive of Mediterranean scrub — is almost always written Olea europaea var. sylvestris. Kew does not accept that name. It records var. sylvestris (Mill.) Lehr as a heterotypic synonym of subsp. europaea, which is to say the register treats the wild olive and the cultivated olive as the same subspecies. The name remains in constant use in the research literature, including in genome work, so you will keep meeting it. It simply is not, at present, an accepted taxon.
How Long Before an Olive Tree Bears — and Why the Crop Swings
An olive is a slow investment. Kew puts it plainly: the tree is slow to mature but can live for hundreds of years. A newly planted grove takes several seasons before it carries anything worth milling, and longer before it repays the planting — which is why olive farming tends to run in families and why groves change hands far less often than arable land does.
The bigger practical issue is what happens after the tree starts bearing. Olives alternate. A heavy crop one season is followed by a light one the next, across whole regions at once, and it is the reason olive oil supply and price move about so much from year to year. The mechanism has been argued over for decades. Shimon Lavee, reviewing the question in Advances in Horticultural Science in 2015, challenged the common assumption that the swing is directly genetic, arguing instead that the metabolic changes producing "on" and "off" years follow from earlier abiotic effects on the tree — that is, from the weather and the growing conditions, not from a fixed internal clock.
For a buyer, the practical consequence is simple enough. A single-harvest oil from a small grove is genuinely finite in a way a blended supermarket oil is not, and a light year is a light year. Our note on single-estate olive oil covers what that constraint buys you and what it costs you.
What the Tree Actually Needs
Olives want a Mediterranean pattern: hot dry summers, mild wet winters, free-draining ground, and a great deal of light. Kew describes the habitat as seasonally dry Mediterranean, or bushland vegetation in the tropics. The tree is famously drought-tolerant, which is not the same as saying it is indifferent to water — a rain-fed tree simply takes what the season gives and yields accordingly.
The limiting factor in cooler countries is not usually cold. Kew's own olives in its Mediterranean Garden survived snow, frost and −7°C in the winter of 2008. What they have not managed is ripening: Kew records that flowers and small fruits have been observed, but the fruit has yet to ripen there. That is the honest answer to whether you can grow an olive tree in Britain. You can grow the tree. Getting a crop worth pressing is a different question, and it is about summer heat rather than winter survival.
How Old Can an Olive Tree Really Get?
This is where most writing about olive trees stops being careful. You will read that a particular tree is 2,000, 3,000 or 4,000 years old, stated flatly. Those figures are estimates, and the honest position is that a living ancient olive is close to undateable.
| Method | What it can establish | Where it falls down |
|---|---|---|
| Counting growth rings | In most temperate trees, one ring per year | Olive wood does not oblige. Cherubini and colleagues found the ring count simply cannot be determined reliably |
| Estimating from trunk girth | A rough figure, if growth rate were constant | It is not constant, and ancient olives grow in near-independent segments that throw the arithmetic out |
| Radiocarbon dating the wood | A firm date for the wood actually sampled | The oldest wood usually rots away; what survives to be sampled is much younger than the tree |
| Genetic analysis | Identity, relatedness, whether the tree is a graft | Says nothing whatever about age |
The dendrochronology is unusually blunt. Paolo Cherubini and colleagues, writing in PLoS ONE in 2013 after a comparative study of olives on Santorini, reported that determining the number of tree rings is impossible in this species, because of intra-annual density fluctuations, variable ring boundaries, and cambial activity that is restricted to shifting sectors of the trunk's circumference — so ring sequences along different radii of the same cross-section disagree with each other.
Radiocarbon does better, and gives a sobering result. Yael Ehrlich and colleagues, in Frontiers in Plant Science in 2017, cut and dated a full olive cross-section and found the oldest radiocarbon-datable material in it was less than 200 years old — in agreement, they noted, with most other radiocarbon dates from the internal wood of living olive trees, which are rarely older than 300 years. They also make the point that a monumental tree cannot be felled to check, and that the inner and oldest wood usually rots out, so the material you would most want to date is precisely the material that is gone.
There is a further complication that is genuinely interesting rather than merely deflating. When Aureliano Bombarely and colleagues sequenced samples from the top and the bottom of the monumental olive of Vouves in Crete — published in Plants in 2021 — they found the two samples had different genetic origins, proving the tree has been grafted at least once. The crown clustered with the Greek cultivar 'Mastoidis'; the rootstock grouped with wild oleasters. So "the age of the tree" is not even a single well-posed question: the trunk and the canopy are, in a real sense, two different plants.
Kew itself is careful here, and it is a good model. Its species profile does not assert an age. It says there are claims of 1,600-year-old trees still producing fruit. We are not going to improve on that hedge, so we will not repeat a figure we cannot source.
The Objections Worth Taking Seriously
The first objection is the obvious one: does any of this reach the bottle? Mostly, no. Subspecies is irrelevant to a shopper — every commercial oil in every shop comes from subsp. europaea, and nothing else is farmed at scale. What does reach the bottle is cultivar, which sets the flavour range, and harvest timing, which sets almost everything else. Our piece on what the colour of an olive oil tells you works through how much of an oil's character is decided by when the fruit came off the tree.
The second objection is aimed squarely at us. Is a rain-fed grove just a grove nobody bothered to irrigate? That deserves a straight answer rather than a slogan. Rain-fed means lower and less predictable yield per tree, and total exposure to the season — in a dry year, you get less oil and there is nothing to be done about it. It is a constraint we accept rather than a technique we invented, and the reason we accept it is that it forces the harvest decision to follow the fruit rather than the calendar. On our grove that has meant picking weeks later than neighbouring farms, once the rains have rehydrated the soil and the fruit has finished maturing on the branch.
The third is about age. If ancient trees cannot be dated, does an old grove mean anything? It means something, but not what the marketing implies. Old trees are typically lower-yielding and harder to harvest; they are kept for character and continuity, not efficiency. "Ancient" on a label is a statement about atmosphere, not about the oil.
From the Tree to the Bottle
Three decisions made in the grove account for most of what you eventually taste. The cultivar sets the palette — how bitter, how peppery, how green or how sweet an oil can possibly be. The harvest date sets the intensity: fruit picked earlier gives less oil per tonne but more polyphenols and more of that peppery catch at the back of the throat, and fruit left to ripen gives more oil and a rounder, milder result. And the interval between picking and pressing sets how much of that survives, because oxidation begins the moment the fruit is bruised.
Everything after that is damage limitation, competently done. Our walkthrough of how olives become extra virgin oil covers the mill end of it, and for what to actually check on a bottle, our guide to choosing a quality olive oil is the practical companion to this one.
Why Sidr & Stone
This article is mostly about trees rather than about us, which is the right proportion. But the reason we can write about grove decisions with any confidence is that ours is a single grove, and we know what was decided in it.
- Single-estate — one family-owned grove on the plains outside Marrakech, Morocco, with no blending across origins.
- Rain-fed — the trees are not irrigated; they take what the season gives them.
- Organically grown — no synthetic fertilisers, pesticides or herbicides.
- Single harvest — a small batch pressed once a season; when it is gone, it is gone until the next one.
- Cold-pressed within hours of harvest — which is what preserves flavour, aroma and polyphenols.
- Unfiltered extra virgin — minimally processed, and it may show natural sediment, which is normal for an unfiltered oil.
- 100% natural — one ingredient, olive oil, with nothing added.
- Dark glass with a gold label — packaging that protects the oil from light.
- Halal certified.
- 10% of profits to charity — a commitment that applies across every Sidr & Stone product.
- Fulfilment in the UK, EU, and US.
We should be equally straight about what we do not publish. We do not currently publish a polyphenol figure, an acidity result or a peroxide value for our oil, because we have not yet had the panel done. Plenty of producers do not publish theirs either, but that is not an excuse, and we would rather say so here than let the silence read as modesty. We will not tell you Sidr & Stone is the best olive oil — that is exactly the sort of unfalsifiable claim this article has spent its length picking apart. What we will say is that the oil is single-estate Moroccan, rain-fed, organically grown and cold-pressed within hours of harvest, and that the evidence of that care is in the taste, the colour and the size of the season's batch.
Frequently Asked Questions
What is the olive oil tree?
It is the olive, Olea europaea L., an evergreen tree in the family Oleaceae first described by Linnaeus in 1753. There is no separate species grown for oil — table olives and oil olives come from the same species, and usually differ only by cultivar and by what the grower does with the fruit.
How long does an olive tree take to produce fruit?
Longer than most fruit crops. Kew describes the olive as slow to mature, and a newly planted grove takes several seasons before it carries a crop worth milling. Exactly how long depends on the cultivar, the rootstock, how the tree was propagated and how well it is watered and fed in its early years.
Why does an olive tree crop heavily one year and barely the next?
This is alternate bearing, and it is characteristic of the species. Shimon Lavee's 2015 review in Advances in Horticultural Science argues the "on" and "off" pattern is set off by earlier environmental conditions acting on the tree rather than being purely genetic. It is the main reason olive oil supply and price move so much from season to season.
How many subspecies of olive tree are there?
Kew's taxonomic backbone currently accepts seven: subsp. europaea, africana, cuspidata, laperrinei, maroccana, guanchica and cerasiformis. You will very often see six quoted, including on Kew's own narrative species page — where a register disagrees with narrative prose, follow the register.
What is the difference between an olive variety and an olive cultivar?
A botanical variety is a naturally occurring form, named under the botanical code. A cultivar is a human selection, named under the separate code for cultivated plants, written in single quotes and maintained as a clone by cutting or graft. 'Picual' and 'Arbequina' are cultivars. Almost everyone calls them varieties, which is loose but rarely causes harm.
How old can an olive tree get?
Honestly, nobody knows. Olive wood cannot be reliably ring-counted, and radiocarbon work on living trees finds datable internal wood rarely older than about 300 years because the oldest heartwood rots away. Kew reports that there are claims of 1,600-year-old trees still fruiting — note that it reports the claim rather than making it.
Can you grow an olive tree in the UK?
You can grow the tree. Kew's own olives came through snow, frost and −7°C in the winter of 2008. Getting ripe fruit is the harder part — Kew records flowers and small fruits at Kew, but the fruit has yet to ripen there. The limit is summer heat rather than winter cold.
Is olive oil a medicine?
No. Olive oil is a food, not a medicine. It has a long traditional history — including being honoured in the Prophetic Sunnah — and a substantial body of modern research, particularly around polyphenols, cardiovascular health, and the Mediterranean diet pattern. It can be a worthwhile part of a healthy routine, but it does not cure diseases and is not a substitute for medical care. Be cautious of any olive oil marketed with specific disease-cure claims.
Final Thoughts
The olive tree rewards attention because it is genuinely strange. It is a single species that has been carried around the world and split into a thousand clonal selections, whose wild ancestor the register will not even grant a separate name, and whose oldest individuals are effectively undateable because the species refuses to lay down countable rings. Almost nothing about it is as tidy as the label copy suggests.
That untidiness is worth carrying into the shop. The number that matters on a bottle is not the age of the trees or the romance of the grove; it is the harvest date, the cultivar, and whether anyone has told you where the fruit was actually grown. Those are checkable. "Ancient groves" is not.
Our cold-pressed organic Marrakech olive oil — single-estate, rain-fed, organically grown and pressed within hours of harvest — is open for pre-order on its limited first harvest. Estimated shipping from November 2026. Fulfilment in the UK, EU, and US.
Pre-Order Sidr & Stone Organic Marrakech Olive Oil — Limited First Harvest →
Disclaimer: This article describes botanical classification and published research at the time of writing; taxonomic opinion and research findings change, and readers should check current sources — Kew's Plants of the World Online is the register used here. Olive oil is a food, not a medicine, and is not a substitute for medical treatment of any condition. For any health concern, consult a qualified medical professional.